JP6418827B2 - Imaging apparatus and control method thereof - Google Patents

Description

The present invention relates to an imaging apparatus and a control method thereof, and more particularly to an imaging apparatus having an autofocus function and a control method thereof .

  2. Description of the Related Art Conventionally, a camera having an autofocus function that automatically recognizes a subject and automatically focuses based on the position of the subject is known.

  As a camera having an autofocus function, there has been proposed a camera that can perform subject recognition with high accuracy by changing a subject recognition algorithm in accordance with an imaging mode (for example, Patent Document 1). Further, there has been proposed a camera that can select a process for increasing the accuracy of the subject position according to the scene and a process that reduces the accuracy but reduces the load (for example, Patent Document 2). According to such a conventional technique, the processing speed is improved by improving an algorithm for recognizing a subject, and a smaller face or a face with an angle can be detected as a subject to be focused. Yes.

  On the other hand, there is a camera that automatically determines the autofocus position and can arbitrarily change the display method for determining and displaying the focus position. As a method of determining and displaying the focus position, there are a pre-display mode and a post-display mode. The prior display mode is a subject display mode in which the subject selected by the camera before the autofocus start instruction is displayed and tracked. On the other hand, the post-display mode is a subject display mode for displaying a subject selected by the camera after an autofocus start instruction.

  The pre-display mode is a mode in which the subject selected by the user or the subject automatically found by the camera is continuously tracked, and is suitable when the target subject is previously captured and determined within the angle of view. In this pre-display mode, the user can switch to another subject before the autofocus operation if the user does not like the main subject that the camera has automatically found. On the other hand, the post-display mode is suitable for photographing that is left to the camera because the camera selects a subject that is likely to be the main from the captured image immediately before photographing even if the target subject does not exist within the angle of view in advance.

JP 2001-330882 A JP 2011-022203 A

  However, in the above prior art, depending on the pre-display mode in which the autofocus target area is displayed before the start of the autofocus operation or the post-display mode in which the autofocus operation is displayed after the start of the operation, the subject recognized by the camera is an object that is not preferable for the user. It becomes a problem. In other words, since the focus position is displayed before shooting in the pre-display mode, if the subject recognized by the camera is undesirable for the user, the user can change to another subject before shooting, which may be a problem. Absent. On the other hand, in the post-display mode, since the focus position is displayed after the start of autofocus, if the subject recognized by the camera is not preferable for the user, there is a possibility that a photo opportunity will be missed if the subject is changed thereafter. As a subject unfavorable for the user, for example, an extremely small face can be cited.

In view of such circumstances, an object of the present invention is to provide an imaging apparatus that can set a subject preferable for a user as a subject to be focused with high probability and a control method thereof .

To achieve the above object, an imaging apparatus comprising: a detection means for detecting a specific object from the images data, the criteria the detecting means sets a criterion for detecting the specific subject A second mode for displaying the autofocus target area after the autofocus start instruction in the first mode for displaying the autofocus target area before the autofocus start instruction. The determination criterion is changed so that the specific subject can be detected more easily than in the case of .

  According to the present invention, the criterion for detecting the subject is changed according to the subject display mode. Therefore, for example, the determination criterion in the mode in which the focus target area is displayed before the autofocus start instruction in which the user can change the main subject is compared with the determination criterion in the mode in which the focus target area is displayed after the autofocus start instruction. Also set it low. This makes it possible to set a subject preferable for the user as a subject to be focused with high probability.

It is a block diagram which shows the structure of the imaging device which concerns on embodiment of this invention. It is the figure which prescribed | regulated the angle of the face in face recognition. 3 is a flowchart illustrating a procedure of autofocus processing to which the imaging apparatus of FIG. 1 is applied. It is a flowchart which shows the procedure of a face position determination process. It is a flowchart which shows the procedure of a face position determination process. It is a flowchart which shows the procedure of the face position determination process in 2nd Embodiment. It is a flowchart which shows the procedure of the face position determination process in 2nd Embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of an imaging apparatus (digital camera) according to an embodiment of the present invention. In FIG. 1, the digital camera 100 includes a power source 110, a card input / output unit 119, and a card slot 120. The power supply 110 supplies power to each circuit in the digital camera 100. The card slot 120 is a place where a memory card 121 as a detachable recording medium is inserted. The memory card 121 is electrically connected to the card input / output unit 119 while being inserted into the card slot 120. In addition to the memory card, a hard disk, an optical disk, a magneto-optical disk, a magnetic disk, or other solid memory may be used as the recording medium.

  The digital camera 100 also includes a CPU 109 that controls the entire digital camera 100, a focusing lens 101, a zooming lens 102, and an aperture 103. The focusing lens 101 performs focus adjustment by advancing and retreating in the optical axis direction. The zooming lens 102 changes the focal length by moving back and forth in the optical axis direction. The diaphragm 103 adjusts the amount of light to the image sensor. The focusing lens 101, the zooming lens 102, and the stop 103 constitute an imaging optical system and are controlled by the CPU 109.

  The digital camera 100 also includes an image sensor 104, a preprocessing circuit 105, an A / D converter 106, an image signal processing device 107, and a frame memory 108. An image sensor 104, a preprocessing circuit 105, an A / D converter 106, an image signal processing device 107, and a frame memory 108 are photoelectric conversion systems that convert an optical image of a subject formed by the imaging optical system into a digital image signal or image data. Configure.

  The image sensor 104 is a photoelectric conversion unit configured by a CCD image sensor, a CMOS image sensor, or the like. The image sensor 104 photoelectrically converts a subject image formed by the imaging optical system including the optical members 101 to 103 and outputs an image signal. The image sensor 104 has an electronic shutter function and can adjust the exposure time. Note that the image sensor 104 may have a mechanical shutter instead of the electronic shutter function and adjust the exposure time. The preprocessing circuit 105 includes a CDS (correlated double sampling) circuit, an AGC (auto gain control) circuit, and the like, and removes noise from the output image signal of the image sensor 104 and controls the gain.

  The A / D converter 106 converts the analog image signal output from the preprocessing circuit 105 into a digital image signal. The image signal processing device 107 performs known image signal processing such as shading correction on the digital image signal by a camera. In other words, the image signal processing device 107 corrects non-linearity in image density due to the characteristics of the image sensor 104 and image color deviation due to the light source. The frame memory 108 functions as a buffer memory that temporarily stores image signals generated by the image sensor 104 to the image signal processing device 107. Although the image data stored in the frame memory 108 has been subjected to correction processing or the like, it can be considered that the electric energy accumulated in each pixel of the image sensor 104 is converted into digital data as it is.

  The CPU 109 transmits a clock signal for controlling the image signal reading of the image sensor 104 and controls the operation timing of the image sensor 104 to the frame memory 108.

  The CPU 109 is connected to a power source 110, a nonvolatile memory 111, a development processing unit 112, a RAM memory 113, a display control device 114, a main switch 116, a first release switch (SW1) 117, and a second release switch 118. The CPU 109 is connected to operation buttons 140 to 142, a card input / output unit 119, a face detection unit 200, a human body detection unit 201, a movement amount calculation unit 202, and an autofocus evaluation value calculation unit 203.

  The nonvolatile memory 111 is composed of an EEPROM or the like, and does not lose recorded data even when the power supply 110 is turned off. The non-volatile memory 111 stores initial camera setting values that are set in the camera when the power source 110 is turned on.

  The development processing unit 112 performs image processing on the RAW data on the frame memory 108 read by the CPU 109 based on the development parameter setting. Each image data subjected to image processing is stored in the RAM memory 113. The development parameter is a parameter related to the image quality of the digital image data, and the white balance, color interpolation, color correction, γ conversion, edge enhancement, and resolution parameters of the digital image data all correspond to the development parameters.

  The RAM memory 113 temporarily stores data when the CPU 109 performs various processes in addition to the image data of the development processing result. The display control device 114 drives and controls the TFT 115 composed of a liquid crystal display element, and outputs image data arranged in the RAM memory 113 in a display image format to the display device. Here, the RAM memory 113 in which an image format for display is arranged is called a VRAM.

  The face detection unit 200 detects a human face as a specific image from the image data, detects facial contours, features of eyes, nose, and mouth as facial parts, and detects the face position, size, and angle (image depth). Direction and image plane direction) and reliability. If there are multiple faces, the position, size, and reliability of the multiple faces are output. The face position is, for example, the coordinates of the origin at the upper left of the input image data. Here, the face detection unit 200 can be set to limit the size of the output face. Faces smaller than the set size are not output.

  FIG. 2 is a diagram defining a face angle in face recognition. As shown in FIG. 2A, the angles in the image depth direction are detected as left 90 degrees 300, left 45 degrees 301, front 302, right 45 degrees 303, and right 90 degrees 304. The face detection unit 200 can be set to limit the angle in the output image depth direction. For example, when only the front surface 302 is set, results other than the front surface 302 are not output. Further, the angles in the image plane direction are detected as 0 degrees 310, 90 degrees 311, 180 degrees 312, and 270 degrees 313 as shown in FIG. The face detection unit 200 can be set to limit the angle in the planar direction that is output. For example, if only 0 degree 310 is set, a result other than 0 degree 310 is not output.

  The reliability output by the face detection unit 200 is, for example, 0 to 255, and the higher the reliability, the higher the possibility of a face. Here, the face detection unit 200 can be set to limit the output reliability. For example, if the reliability is set to 128, a face with a reliability lower than 128 is not output.

  The human body detection unit 201 recognizes a human type (a silhouette from the head to the shoulder) from the image data, and outputs the position, size, and reliability of the face. The reliability output by the human body detection unit 201 is, for example, 0 to 255, and the higher the reliability, the higher the possibility that the human body is a human body. Here, as with the face detection unit 200, the human body detection unit 201 can also perform settings for limiting the output result for the size and reliability of the face.

  When the movement amount calculation unit 202 inputs the first image data, the second image data, and the designated area (designated by coordinates and size) for the first image data, the designated area of the first image data becomes the first image data. The amount of movement to which region of the image data 2 has been moved is calculated. By applying the movement amount calculation unit 202, it is possible to track the area determined to be the main subject.

  An AF evaluation value calculation unit 203 calculates an autofocus evaluation value by designating image data and a position from which the evaluation value is acquired. The CPU 109 can perform an autofocus operation by driving the focusing lens 101 based on the AF evaluation value. The autofocus operation includes a contrast method and a phase difference method, but the method is not particularly limited here.

  When the user turns on the main switch 116, the CPU 109 executes a predetermined program. When the user turns off the main switch 116, the CPU 109 executes a predetermined program and puts the camera into a standby mode. The first release switch (SW1) 117 is turned on by the first stroke (half-pressed state) of the release button, and the second release switch 118 is turned on by the second stroke (full-pressed state) of the release button. The autofocus operation starts when the first release switch (SW1) 117 is turned on. The imaging operation starts when the second release switch 118 is turned on.

  When the CPU 109 detects that the left selection button 140, the right selection button 141, and the setting button 142 are pressed, the CPU 109 performs control according to the operation state of the digital camera 100. When live view is selected from the menu, RAW data is fetched from the image sensor 104 periodically, for example, 30 times per second, developed, processed, and distributed to the VRAM, thereby displaying an image captured from the image sensor 104 in real time. . Also, the subject display mode during live view can be switched from the menu. The subject display mode includes a pre-display mode and a post-display mode, and the user can switch the method for determining the display timing and position of the autofocus operation position during live view by switching the mode. The prior display mode is a mode in which the autofocus target area is displayed on the TFT 115 before the user gives an autofocus start instruction (before the first release switch 117 is turned on). Further, the post-display mode is a mode in which the camera determines a position where autofocus is performed after an autofocus start instruction.

  In the prior display mode, for example, the face position obtained by integrating the detection results using the face detection unit 200, the human body detection unit 201, and the movement amount calculation unit 202 is displayed as the autofocus position. When a plurality of faces are detected, the camera selects and displays one of them. When the user wants to change the main subject to a face different from the face at the currently displayed autofocus position, the user can switch to another face by pressing the left selection button 140 or the right selection button 141. it can.

  Hereinafter, autofocus processing during live view to which the imaging apparatus (digital camera) of FIG. 1 is applied will be described.

  FIG. 3 is a flowchart illustrating a procedure of autofocus processing to which the imaging apparatus (digital camera) of FIG. 1 is applied. This autofocus process is executed by the CPU 109 of the digital camera 100 in accordance with a program stored in a ROM (not shown). This process is an autofocus process in the live view that is executed simultaneously with the start of the live view.

  In FIG. 3, when the autofocus process is started, the CPU 109 determines whether or not the subject display mode is the prior display mode (step S401). As a result of the determination in step S401, when the pre-display mode is set (“YES” in step S401), the CPU 109 determines whether there is a face position determined in the face position determination process in FIGS. 4A and 4B described later. Is determined (step S402). As the face position, any face position determined by the face position determination process is stored in the RAM memory 113 and used. As a result of the determination in step S402, if there is a determined face position (“YES” in step S402), the CPU 109 performs a writing process to the VRAM 113 to display the face position on the TFT 115, and displays a face frame at the face position. (Step S403). At this time, the face position is displayed with a white frame, for example.

  After displaying the face position as a white frame, the CPU 109 determines whether or not the first release switch (SW1) 117 is on (step S404). If the result of the determination in step S404 is that the first release switch (SW1) 117 is on (“YES” in step S404), the CPU 109 sets the face position displayed with a white frame as the position for acquiring the autofocus evaluation value. (Step S405).

  After setting the position for acquiring the autofocus evaluation value, the CPU 109 executes an autofocus operation based on the autofocus evaluation value (step S406). Next, when it is determined that the result of the autofocus operation is in focus, the CPU 109 displays the focus position from which the evaluation value has been acquired, for example, with a green frame (step S407). At this time, if it cannot be determined that the focus is achieved, nothing is done.

  After displaying the focus position in a green frame, the CPU 109 determines whether or not the first release switch 117 (SW1) is off, and if not, waits until it is off (step S408). On the other hand, if the result of determination in step S408 is that the first release switch (SW1) 117 is off (“YES” in step S408), the CPU 109 returns the process to step S401.

  On the other hand, as a result of the determination in step S402, when there is no face position determined before that ("NO" in step S402), the CPU 109 determines whether or not the first release switch (SW1) 117 is on ( Step S409). If the result of determination in step S409 is that the first release switch 117 (SW1) is on (“YES” in step S409), the CPU 109 advances the process to step S410. That is, the CPU 109 performs a distance measurement operation, sets the center of the object (subject) at the closest distance as a position for acquiring the autofocus evaluation value (step S410), and then advances the processing to step S406. If the result of determination in step S409 is that the first release switch (SW1) 117 is off (“NO” in step S409), the CPU 109 returns the process to step S401.

  When the first release switch (SW1) 117 is OFF (“NO” in step S404) as a result of the determination in step S404, the CPU 109 performs processing similar to the case where the determination result in step S409 is “NO”. Is returned to step S401.

  On the other hand, if the result of determination in step S401 is not the pre-display mode (“NO” in step S401), that is, if the post-display mode is set as the subject display mode, the CPU 109 advances the processing to step S411. That is, the CPU 109 determines whether or not the first release switch (SW1) 117 is on (step S411). If the result of the determination in step S411 is that the first release switch (SW1) 117 is on (“YES” in step S411), the CPU 109 determines whether there is a face position previously determined in the face position determination process. (Step S412).

  If the determined face position exists as a result of the determination in step S412 (“YES” in step S412), the CPU 109 advances the process to step S413. That is, the CPU 109 sets the face position determined in the face position determination process as a position for acquiring the autofocus evaluation value, and then advances the process to step S406.

  On the other hand, if the result of determination in step S 412 is that there is no previously determined face position (“NO” in step S 412), the CPU 109 advances the process to step S 414. That is, the CPU 109 performs a distance measurement operation, sets the center of the object (subject) at the closest distance as a position for acquiring the autofocus evaluation value, and then advances the processing to step S406. If the result of determination in step S411 is that the first release switch 117 (SW1) is not on, the CPU 109 returns the process to step S401.

  According to the processing of FIG. 3, when there is a face position that has been determined before, after displaying the face frame at the face position in the pre-display mode, it is determined whether or not SW1 is on in the post-display mode. If it is on, the previously determined face position is determined as the autofocus evaluation value acquisition position. On the other hand, if there is no previously determined face position, the center of the subject at the closest distance is set as the autofocus evaluation value acquisition position in the current face position detection process in any mode. This makes it easy to set the subject position that the user wants to be the main subject as the position for acquiring the autofocus evaluation value while referring to the previous operation and the live view screen, and the convenience is improved.

  Next, the face position determination process for determining the face position to be determined in step S402 in the autofocus process of FIG. 3 will be described.

  4A and 4B are flowcharts illustrating the procedure of the face position determination process. This face position determination process is executed by the CPU 109 of the digital camera 100 in accordance with a program stored in a ROM (not shown).

  The face position determination process is started when the live view is started, and is executed every time an image is acquired, as in the above-described autofocus process. For face detection and human body detection, processing is performed using an image acquired at the time of processing, and for movement amount calculation processing, processing is performed using an image acquired at the time of processing and an image at the previous processing before that. Done.

  4A and 4B, when the face position determination process is started, the CPU 109 first determines whether or not the subject display mode is the preliminary display mode (step S101). As a result of the determination in step S101, when the pre-display mode is set (“YES” in step S101), the CPU 109 sets the setting value for the pre-display mode as the minimum detection size in the face detection unit 200 and the human body detection unit 201. Is set (step S102). The setting value of the minimum detection size is a setting value unique to each image display mode. That is, the setting value of the minimum detection size for the pre-display mode is stored in advance in a ROM (not shown) of the digital camera 100, as is the setting value of the minimum detection size for the post-display mode described later. Is used. In addition, the setting value of the face angle in the depth direction for the pre-display mode, the setting value of the face angle in the plane direction for the pre-display mode, and the setting value of the face reliability for the pre-display mode set in the following processing Is also a setting value specific to the pre-display mode, and is stored in advance in a ROM (not shown).

  After setting the minimum detection size for the face detection unit 200 and the human body detection unit 201, the CPU 109 sets the setting value for the pre-display mode as the face angle in the depth direction in the face detection unit 200 (step S103).

  After setting the face angle in the depth direction, the CPU 109 sets the setting value for the pre-display mode in the face detection unit 200 as the face angle in the plane direction (step S104). Next, the CPU 109 sets the setting value of the face reliability for the prior display mode as the reliability in the face detection unit 200 and the human body detection unit 201 (step S105).

  Next, the CPU 109 sets the current image in the face detection unit 200 and starts face detection (step S106), and sets the current image in the human body detection unit 201 and starts human body detection (step S107). ). After starting the human body detection, the CPU 109 determines whether or not there is a previously determined face position (step S108). As a result of the determination in step S108, when there is a face position determined last time (“YES” in step S108), the CPU 109 sets the previously determined face position as a reference position for calculating the movement amount in the movement amount calculation unit 202. (Step S109). Next, the CPU 109 sets the previous image and the current image and starts calculating the movement amount of the current face position with respect to the previous face position (step S110).

  Next, the CPU 109 determines whether or not the movement amount has been calculated, and waits until the calculation is completed (step S111). Then, after the calculation of the movement amount is completed (“YES” in step S111), the CPU 109 determines whether face detection and human body detection are completed, and waits until completion (step S112). When the face detection and the human body detection are completed as a result of the determination in step S112 ("YES" in step S112), the CPU 109 determines whether or not there is an instruction to change the face from the user (step S113). If the result of determination in step S113 is that there is a face change instruction from the user (“YES” in step S113), the CPU 109 advances the process to step S114. That is, the CPU 109 invalidates the movement amount calculation result and the previous face position detection result acquired in steps S110 to S111, and deletes the result corresponding to the previous face position from the face detection result and the human body detection result (step S114). .

  Here, the result corresponding to the previous face position is a face detection result closest to the previous face position within one-sixth of the horizontal size of the detected image, and this time refers to the face position determined last time. This is a face detection result to be determined as a face position in the face position determination process. That is, when the detected image size of the previous face is, for example, vertical 480 pixels × horizontal 640 pixels, the currently detected face position that is within 1/6 of the horizontal size 640 pixels from the center of the detected image, that is, within 106 pixels. Corresponds to the face corresponding to the center closest to the center of the previous face position. Similarly, in the vertical direction, the face corresponding to the center closest to the center of the previous face position among the centers of the face positions detected this time at a distance of 1/6 of 480 pixels, that is, within 80 pixels, is shown. The result corresponds to the current face position. Therefore, it is sufficient to satisfy either the vertical or horizontal condition.

  Next, the CPU 109 determines the face position (step S115). That is, if there is a previous face position result, if there is a face or human body detection result closest to the previous face position result within one-sixth of the detected image size, the CPU 109 determines the face position or the human body. The detection position is determined as the current face position. On the other hand, if there is no face or human body detection result closest to the previous face position result within 1/6 of the detected image size, the movement amount calculation result is set as the face position detection result. Further, when neither the face detection unit 200 nor the human body detection unit 201 can detect the face or the human body, and the movement amount calculation unit 202 cannot calculate the movement amount, the CPU 109 does not have a suitable face as the face position detection result. And decide. Further, if there is no previous face position detection result, the CPU 109 determines the most reliable face detection result among the currently detected face positions as the face position, and if there is no face detection result detected this time, the face position is determined. No detection result. Then, the CPU 109 stores the detection result in the RAM memory 113, and then returns the process to step S101.

  Note that if the result of determination in step S108 is that there is no previously determined face position (“NO” in step S108), the CPU 109 advances the process to step S112. If the result of determination in step S113 is that there is no face switching instruction from the user (“NO” in step S113), the CPU 109 advances the processing to step S115.

  On the other hand, if the result of determination in step S101 is that the subject display mode is not set to the pre-display mode (“NO” in step S101), that is, the post-display mode, the CPU 109 advances the processing to step S116. That is, the CPU 109 sets a setting value for the post-display mode as the minimum detection size in the face detection unit 200 (step S116). The setting value of the minimum detection size for the post-display mode set in the face detection unit 200 is a setting value specific to the post-display mode stored in advance in the ROM (not shown) of the digital camera 100, and the set value is used. At this time, the minimum detection size for the post-display mode is set larger than the minimum detection size for the pre-display mode. In addition, the setting value of the face angle in the depth direction for the posterior display mode, the setting value of the face angle in the plane direction for the posterior display mode, and the setting value of the face reliability for the posterior display mode set in the following processing Is also a setting value specific to the post-display mode, and is stored in advance in a ROM (not shown).

  After setting the minimum detection size for the face detection unit 200, the CPU 109 sets a setting value for the posterior display mode as the face angle in the depth direction in the face detection unit 200 (step S117). At this time, the face angle range in the depth direction for the post-display mode is defined to be narrower than the face angle range in the depth direction for the prior display mode.

  After setting the face angle in the depth direction, the CPU 109 sets the setting value for the posterior display mode as the face angle in the plane direction in the face detection unit 200 (step S118). At this time, the face angle range in the planar direction for the post-display mode is defined to be narrower than the face angle range in the planar direction for the prior display mode. Next, the CPU 109 sets a face reliability setting value for the post-display mode in the face detection unit 200 (step S119). At this time, the reliability setting value for the post-display mode is defined to be higher than the reliability setting value for the pre-display mode.

  Next, the CPU 109 sets the current image in the face detection unit 200 and starts face detection (step S120). After starting the face detection, the CPU 109 determines whether the face detection is completed and waits until it is completed (step S121). When the face detection is completed as a result of the determination in step S121 (“YES” in step S121), the CPU 109 determines the face detection result with the highest reliability among the face positions detected this time as the face position, and detects the face. If there is no result, it is determined that there is no face position result (step S122). Then, the CPU 109 stores the detection result in the RAM memory 113, and then returns the process to step S101.

  In this face position determination process, a setting value of a criterion for determining the face position is stored in advance in a ROM (not shown) of the digital camera 100 according to the subject display mode, and this setting value is used. At this time, the minimum detection size in the post-display mode in face detection and human body detection is defined to be larger than the minimum detection size in the prior display mode. Further, the face angle range in the depth direction and the image plane direction of the face detection for the post-display mode is defined to be narrower than the face angle range for the pre-display mode. Specifically, when the face angle in the depth direction in the pre-display mode is all of left 90 degrees 300, left 45 degrees 301, front 302, right 45 degrees 303, and right 90 degrees 304, in the post-display mode, Only 45 degrees 301 left, 302 front, and 45 degrees right 303 are defined. On the other hand, when the face angle in the plane direction in the pre-display mode is all of 0 degrees 310, 90 degrees 311, 180 degrees 312, and 270 degrees 313, in the post-display mode, for example, only 0 degrees 310 is defined. In addition, the reliability for the post-display mode is specified to be higher than the reliability for the pre-display mode, and the post-display mode is set to detect only results with higher reliability than the pre-display mode. ing.

  According to the processing of FIGS. 4A and 4B, the determination criterion setting for determining the face position in the post-display mode is made stricter than the determination criterion setting for determining the face position in the pre-display mode. Accordingly, in the post-display mode in which it is difficult for the user to change the focus target, the face that is the subject intended by the user is easily set as the focus target.

  On the other hand, in the prior display mode in which the user can change the focus target, the face position is used as the focus position even when the possibility of being a face is relatively low. In this case, there is a possibility that a face position that is not intended by the user may be determined as a focus target. In such a case, the user can change the setting of the face position. This makes it easy to set a user-desired subject as a subject to be focused, and allows autofocus processing during live view to be performed quickly.

  In the present embodiment, the subject display mode is set in the digital camera 100 by the user in advance using a subject display mode setting unit (not shown).

  Further, in the present embodiment, the calculation result of the movement amount calculation unit 202 is adopted as a criterion for detecting a face in the prior display mode, but is a criterion for detecting a face in the post-display mode. Not adopted as. This is because, in the post-display mode, the determination criteria are set more strictly than in the pre-display mode, and thus the face position data determined last time is not referred to.

  In the present embodiment, an example in which a face is detected using all of the face detection unit 200, the human body detection unit 201, and the movement amount calculation unit 202 has been described. However, the present invention is not limited to this. . In the post-display mode, only a part of the face detection unit 200, the human body detection unit 201, and the movement amount calculation unit 202 may be used if the determination criteria are set stricter than in the pre-display mode. Further, although an example has been given in which a face is detected as an object to be autofocused, a configuration for detecting a subject other than a face may be used as long as the criterion is set stricter than in the prior display mode.

  Hereinafter, a second embodiment will be described.

  In the present embodiment, the autofocus process is executed in the same manner as the process of FIG. 3 in the first embodiment, and only the face position determination process is different from the first embodiment.

  FIG. 5A and FIG. 5B are flowcharts illustrating the procedure of the face position determination process in the second embodiment. This face position determination process is executed by the CPU 109 of the digital camera 100 in accordance with a program stored in a ROM (not shown).

  In the present embodiment, the autofocus process is the same as that in the above embodiment, and thus the description thereof is omitted. The face position determination process is started when the live view is started, and is executed every time an image is acquired during the live view, as in the above embodiment.

  5A and 5B, when the face position determination process is started, the CPU 109 first sets a minimum detection size for the face detection unit 200 and the human body detection unit 201 (step S501). At this time, as the minimum detection size, a setting value for the prior display mode that is a detection target up to a smaller face size is set. The setting value of the minimum detection size is a setting value specific to the display mode that varies depending on the subject display mode, and the setting value of the minimum detection size of the prior display mode is stored in advance in the ROM of the digital camera 100. Value is applied. Also, the setting value of the face angle in the depth direction for the pre-display mode, the setting value of the face angle in the plane direction for the pre-display mode, and the setting value of the face reliability for the pre-display mode set in the following processing Is also a setting value specific to the pre-display mode, and is stored in advance in a ROM (not shown). Each set value in the post-display mode is also stored in advance in a ROM (not shown).

  After setting the minimum detection size for the face detection unit 200 and the human body detection unit 201, the CPU 109 sets the face angle in the depth direction for the face detection unit 200 (step S502). At this time, as the face angle in the depth direction, an angle range for the pre-display mode having a wider detection angle range than the post-display mode is set.

  After setting the face angle in the depth direction, the CPU 109 sets the face angle in the plane direction for the face detection unit 200 (step S503). At this time, as the face angle in the planar direction, an angle for the pre-display mode having a wider detection angle range than the post-display mode is set. Next, the CPU 109 sets reliability for the face detection unit 200 (step S504). At this time, the reliability is set to a reliability setting value for the pre-display mode, which is lower in reliability than the post-display mode.

  After setting the reliability, the CPU 109 sets the current image in the face detection unit 200 and starts face detection (step S505). Next, the CPU 109 sets the current image in the human body detection unit 201 and starts human body detection (step S506). After starting the human body detection, the CPU 109 determines whether or not there is a previously determined face position (step S507). As a result of the determination in step S507, when there is a face position determined last time (“YES” in step S507), the CPU 109 instructs the movement amount calculation unit 202 to use the face position determined last time as a reference position for calculating the movement amount. (Step S508). Next, the CPU 109 sets the previous image and the current image and starts calculating the movement amount (step S509).

  Next, the CPU 109 determines whether or not the movement amount has been calculated, and waits until the calculation is completed (step S510). Then, after the calculation of the movement amount is completed (“YES” in step S510), the CPU 109 determines whether face detection and human body detection are completed, and waits until completion (step S511). As a result of the determination in step S511, after the face detection and the human body detection are completed (“YES” in step S511), the CPU 109 determines whether or not there has been a face change instruction from the user (step S512). If the result of determination in step S512 is that there is a face change instruction from the user (“YES” in step S512), the CPU 109 advances the process to step S513. That is, the CPU 109 invalidates the movement amount calculation result and the previous face position detection result acquired in steps 509 to S510, and excludes the result corresponding to the previous face position from the face detection result and the human body detection result (step S513). . Here, the result corresponding to the previous face position is the face closest to the previous face position within 1/6 of the horizontal size of the detected image.

  Next, the CPU 109 determines whether or not the pre-display mode is set as the subject display mode (step S514). If the pre-display mode is set as a result of the determination in step S514 (“YES” in step S514), the CPU 109 determines the face position (step S515). That is, if there is a previous face position result, if there is a face or human body detection result closest to the previous face position result within 1/6 of the detected image size, the CPU 109 detects the face position or human body detection. The position is determined as the current face position. On the other hand, if there is no face or human body detection result closest to the previous face position result within 1/6 of the detected image size, the movement amount calculation result is set as the face position detection result. In addition, when neither the face detection unit 200 nor the human body detection unit 201 can detect the CPU 109 and the movement amount calculation unit 202 cannot calculate the movement amount, the CPU 109 determines that there is no suitable face as the face position detection result. If there is no previous face position detection result, the CPU 109 determines the face detection result with the highest reliability among the face positions detected this time as the face position. If there is no face detection result detected this time, the CPU 109 detects the face position. No result. Then, the CPU 109 stores the detection result in the RAM memory 113, and then returns the process to step S101.

  As a result of the determination in step S507, if there is no face position determined last time (“NO” in step S507), the CPU 109 advances the process to step S511. If the result of determination in step S512 is that there is no face switching instruction from the user (“NO” in step S512), the CPU 109 advances the process to step S514.

  On the other hand, if the result of determination in step S514 is that the subject display mode is not the pre-display mode but the post-display mode (“NO” in step S514), the CPU 109 advances the process to step S516. In other words, the CPU 109 deletes from the detection result a face whose size is not recognized as a face in the post-display mode and a reliability level that is not recognized as a face from the detection result of the face detection unit 200 (step S516). Here, in this process, as in the first embodiment described above, a face that is smaller in face detection in the pre-display mode than in the post-display mode is set as a detection target. In addition, regarding the reliability, even faces whose reliability is lower in the pre-display mode than in the post-display mode are set as detection targets. Therefore, these detection results are excluded from the determination targets, and detection with higher accuracy is performed.

  Next, the CPU 109 determines the face detection result with the highest reliability as the face position, and determines that there is no face position when there is no face detection result (step S517). The CPU 109 stores the determined face position in the RAM memory 113 and then returns the process to step S501.

  5A and 5B, the determination criteria for the pre-display mode with a wider detection range are commonly set as the determination criteria to be set in the face detection unit 200, the human body detection unit 201, and the movement amount calculation unit 202. . And only in the case of the post-display mode, a process for excluding results outside the detection range after detection is added. This eliminates the need for control to change the determination criterion for each parameter depending on the subject display mode. Therefore, the complexity of design and the complexity of operation can be reduced as compared with the first embodiment, and the same effect can be obtained.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the meaning.

100 Digital Camera 101 Focusing Lens 109 CPU
111 Nonvolatile memory 113 RAM memory 114 Display control device 115 TFT
117 First release switch 118 Second release switch 200 Face detection unit 201 Human body detection unit 202 Movement amount calculation unit 203 Autofocus evaluation value calculation unit

Claims (9)

Detection means for detecting a specific object from the images data,
A reference setting means for setting a determination reference for the detection means to detect the specific subject,
In the first mode in which the autofocus target area is displayed before the autofocus start instruction is given, the reference setting means is more specific than in the second mode in which the autofocus target area is displayed after the autofocus start instruction is given. An image pickup apparatus , wherein the determination criterion is changed so that a subject can be easily detected . The specific subject is a human face;
It said sensing means, the imaging apparatus according to claim 1, characterized in that the face detection means. The detection means, in the first mode, using the face detection means and the human body detecting means detects the specific subject, the in the second mode, the face without using the human body detecting means imaging device according to claim 1, wherein the detecting the specific subject using detection means. Said reference setting means, before the minimum detectable size of a particular object dangerous knowledge means the detection target in the first mode, the minimum detectable size of the specific subject to be detected in the second mode smaller than Kunar so on, the image pickup apparatus according to any one of claims 1 to 3, characterized in that to set the criteria. Said reference setting means, before the angular range in the depth direction of the specific object that dangerous knowledge means the detection target in the first mode, the depth of the specific subject to be detected in the second mode a wide Kunar so than in the direction of the angle range, the image pickup apparatus according to any one of claims 1 to 4, characterized in that to set the criteria. Said reference setting means, before said specific image plane direction of the angle range of the subject dangerous knowledge means the detection target in the first mode, the specific subject to be detected in the second mode a wide Kunar so than the angular range of the image plane direction, the imaging apparatus according to any one of claims 1 to 5, characterized in that for setting the judgment criteria. It said reference setting means, the reliability of the specific subject before dangerous knowledge means the detection target in the first mode, than the reliability of the specific subject to be detected in the second mode low Kunar so on, the image pickup apparatus according to any one of claims 1 to 6, characterized in that to set the criteria. A calculation means for calculating a movement amount indicating to which area the designated area in the first image has moved in the second image;
The reference setting means adopts the calculation result of the calculation means as the determination criterion in the first mode, but does not adopt the calculation result of the calculation means as the determination reference in the second mode. The image pickup apparatus according to claim 1 , wherein the image pickup apparatus is a feature. A detection process for detecting a specific subject from image data;
A reference setting step for setting a determination reference for detecting the specific subject in the detection step,
In the reference setting step, in the first mode in which the autofocus target area is displayed before the autofocus start instruction, the specific mode is compared with the second mode in which the autofocus target area is displayed after the autofocus start instruction. A method for controlling an image pickup apparatus, wherein the determination criterion is changed so that a subject of the subject can be easily detected.

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